Enhanced dedicated-channel reporting for umts

ABSTRACT

A method for a mobile communication system, the mobile communication system defining a dedicated channel (DCH) active set and an enhanced-dedicated channel (E-DCH) active set, the method including performing a power measurement of a pilot signal from a cell that is not included in the E-DCH active set but included in the DCH active set, and performing a power measurement of a pilot signal from a cell that is included in the E-DCH active set.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation application of U.S. patentapplication Ser. No. 11/662,490, filed on Mar. 15, 2007, which is basedon and claims priority from Patent Cooperation Treaty ApplicationPCT/JP2006/322207 filed on Oct. 31, 2006, which is based on and claimspriority from United Kingdom Patent Application No. 0522185.8, filed onOct. 31, 2005, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The subject invention relates to UMTS (Universal MobileTelecommunications System) communication and, more particularly, to UMTScommunication that uses not only a superset of dedicated radio links butalso simultaneously uses a subset of enhanced dedicated radio links.

This application is based upon and claims the benefit of priority fromUK patent application No. 0522185.8, filed on Oct. 31, 2005, thedisclosure of which is incorporated herein in its entirety by reference.

BACKGROUND ART

Cellular telephone communications have greatly advanced since the firstsystem became operational in Japan in 1979. These first-generationsystems were analogue. By the end of the 1980's the technology had movedto second-generation digital systems for two reasons. Firstly, analoguesystems in use became incompatible with each other, and secondly, it wasmore economic to operate digital systems. In the early 1990's varioussecond-generation systems were introduced. In Europe, GSM (Global Systemfor Mobile Communications) was introduced. The United States introduceda second-generation system (AMPS) different from GSM, although itsubsequently introduced a modified GSM.

GSM represents an interface between cellular phones (User Equipment:UEs) and a Core Network (CN). The interface includes a series of RadioNetwork Controllers (RNCs), with each RNC connected to a series of BaseStations (BSs), each of which in turn transmits and receives to UEswithin its broadcast range. At any one time a UE sends and receivessignals to one of the RNCs through only one of the BSs. As a UE movesaround under GSM a “hard handover” takes place between one base stationand another. The UE is constantly monitoring the power level ofrespective pilot channel signals received from the current BS andin-range BSs, and is sending resulting power comparison data in signalsthrough the present BS to the RNC controlling the current BS. When theRNC determines that a signal from one of the in-range BSs is beingreceived by the UE at a power level greater by at least a thresholdamount over the power level of the current BS, the RNC directs the UE tostart communicating with that one of the in-range BSs and to ceasecommunicating with the current BS. The handover is called a “hardhandover” because the UE ceases transmitting to the one BS for a veryshort interval before it starts transmitting to the new BS; there is no“soft” transition involving communication with both BSs simultaneously.

With the tremendous growth in cellular phone services and the increaseddemand to use them for “roaming”, the need for a universal standardbecame recognized. Technology was at the same time improving, so this“third-generation” system could incorporate improved technology, andintegrate telecommunications features with those of Internet Protocol(IP) networks. UMTS primarily only differs from GSM in the communicationbetween the RNC level and the UE level; the CN remains essentially thesame as with GSM. Instead of communication of a UE through a single BSat any one time, UMTS uses UTRAN (Universal Terrestrial Radio AccessNetwork) consisting of a network in which RNCs communicate with a seriesof nodes (nodeBs) simultaneously. Each nodeB supports one or more“cells” each of which has a signal coverage area, and the UEcommunicates with the cell or cells from a series of nodeBs.

Instead of handover of a UE from one BS to another BS as in GSM,mobility of the UE causes a continuing change in those nodeBs by whichthe UE communicates with the RNC, e.g. some are dropped as others arepicked up. A “UMTS UE” is capable of receiving and transmitting througha communication path that involves simultaneous operation of all of thecells through which the UE passes, the UE and the RNC being atrespective opposite ends of a communication path that uses the cells.UMTS results not only in a unified universal standard for UEmanufacturers, but its signal transmission and reception diversityresults also in improved signal quality. GSM is meanwhile still also inuse, with UMTS and GSM existing side-by-side in many locations to allowpersons with either type of UE to effectively use their mobile phones.In the CN, UMTS and GSM communications are similar; as indicatedearlier, the two systems differ mainly in how communication proceedsbetween the RNCs and the UEs.

In comparison to the “hard handover” used in GSM, UMTS uses “softhandover”. There also exists what is termed “softer handover”, but forpurposes of this invention it is sufficient to only describe “softhandover”. As mentioned above, a UMTS UE operates with acontinuously-updated set of cells through which it is receiving andtransmitting to its RNC. The criteria for cells entering and leavingwhat is termed the “Active Set” of cells is known. A general descriptionis provided, for instance, in “Radio Network Planning and Optimisationfor UMTS” by Laiho, Wacker and Novosad. Cell addition, removal orreplacement are three of the six categories of “Events” recognized underUMTS. Addition of a cell is termed “an Event 1a”, removal of a cell istermed “an Event 1b”, and replacement of a cell with another cell istermed “an Event 1c”. The addition, removal or replacement of cells iseach dependent on differential power-level measurements between pilotsignals of respective cells. Such measurements are taken periodically bythe UE and transmitted to its RNC for appraisal. If the RNC deter-minesthat the criteria is satisfied for adding, removing or replacing one ofthe cells through which the UE is communicating, the RNC sends a signalto the UE to take necessary actions to either start or terminatecommunication with a cell, or to both start communication with one cellwhile terminating communication with another. FIG. 1 shows the equationsinvolved in determining the Events 1a and 1b, and indicates the factorsinvolved in that determination.

DISCLOSURE OF THE INVENTION

The set of cells mentioned above will henceforth be termed the “supersetof cells” or “superset cells” for the particular UE. The subjectinvention relates to communication of a UE not only with its supersetcells but also with a second set of cells which will be termed the“subset of cells” or “subset cells”. As is illustrated in FIG. 2, allsubset cells are also superset cells but not all superset cells aresubset cells. As with superset cells which are being continuouslyexchanged (indicated by I) with non-superset cells of the UMTS networkas the UE roams, superset cells may also join and leave the subset.

A conventional UMTS UE may simply require a software upgrade so as to beable to differentiate between superset cells and subset cells.Similarly, a RNC may only require a minor software upgrade. Examples ofthe enhanced capabilities provided by subset cells over those ofsuperset cells are: (i) higher data rates for data transmission, and(ii) closer transmission and reception intervals. A subset cell is ableto transmit and receive at the higher data rates and the closertransmission intervals as well as at the “normal” data rates andtransmission intervals of the superset cells. However, superset cellsare not able to communicate with the UE at the higher data rates orcloser transmission intervals of the subset cells. A subset-capable cellis a superset cell which is capable of higher data rates and closertransmission intervals, i.e. enhanced communication, but iscommunicating with the UE at the “normal” data rates and transmissionintervals of the superset cells. The subject invention is involved withthe transition of some superset cells to be subset cells and with theirtransition back to superset cells. It should be noted that the currentsuperset and subset cells are also referred to, respectively, as the DCH(Dedicated Channel) Active Set (DAS) and the E-DCH (Enhanced DedicatedChannel) Active Set of cells (EAS).

A problem has existed that downlink Event-triggered measurement reportscan only be configured (measured by the UE) on a superset-cell basis andnot also on a subset-cell basis. Thus a problem is not in determiningmembership of the superset, but rather in determining which of thesuperset cells are also subset cells. For the purpose of powermeasurements, conventional UEs only recognize the difference betweenin-range cells and superset cells; they cannot recognize the differencebetween those superset cells that are not also subset cells, i.e.subset-capable cells, and those superset cells that are also subsetcells. The RNC knows the difference, but the difference is notcommunicated to the UE. One embodiment may alleviate this problem, sincea UE that has knowledge of (i) which cells are superset cells only, (ii)which cells are superset cells that are subset-capable cells, and (iii)which cells are subset cells (in addition to being superset cells) canuse that information in taking power measurements that can be used todetermine when subset cells should be added, removed or exchanged withother subset cells. A related problem involves the situation where anin-range cell becomes a superset cell and where it is eligible to alsobecome a subset cell.

In one form of a first aspect, the subject invention provides a methodfor Universal Mobile Telecommunications System (UMTS) communicationutilizing User Equipment (UE) and a Radio Network Controller (RNC) forcommunicating with the UE through a changing set of cells. The methodincludes periodically performing the steps of: measuring at the UE thepower in received pilot signals from in-range cells; deter-mining whichof in-range cells are to be included in communication to the UE(superset cells), an in-range cell being determined to be a supersetcell if the UE-received pilot-signal power is above a superset powerthreshold; determining whether any of the superset cells is also asubset cell capable of providing enhanced UE communication, a supersetcell being determined to be also a subset cell if: that superset cell isknown to have the capability of also being a subset cell; and, thenumber of existing subset cells is below a predetermined maximum numberof subset cells.

The method may include the step of using the determined result fordetermining what to include in the next power measurement at the UE.

In another form, the subject invention provides a method performed by aRadio Network Controller (RNC) of a Universal Mobile TelecommunicationsSystem (UMTS). The method includes periodically performing the steps of:receiving from User Equipment (UE) measurement of power in pilot signalsof cells; determining which of in-range cells are to be included incommunication to the UE (superset cells), an in-range cell beingdetermined to be a superset cell if the UE-received pilot-signal poweris above a superset power threshold; determining whether any of thesuperset cells is also a subset cell capable of providing enhanced UEcommunication, a superset cell being determined to be also a subset cellif: that superset cell is known to have the capability of also being asubset cell; and, the number of existing subset cells is below apredetermined maximum number of subset cells.

The method may further include the step of transmitting the determinedresult to the UE. The determined result may include information on eachcell as to whether the category of the cell is in-range cell, supersetcell, subset-capable cell or subset cell, that information being used bythe UE for determining what to include in the next power measurement.

In a further form, the subject invention provides a method performed byUser Equipment (UE) of a Universal Mobile Telecommunications System(UMTS). The method includes periodically performing the steps of:measuring power in cell pilot signals, the measurements allowing for:determining which of in-range cells are to be included in communicationto the UE (superset cells), an in-range cell being determined to be asuperset cell if the UE-received pilot-signal power is above a supersetpower threshold; and, determining whether any of the superset cells isalso a subset cell capable of providing enhanced UE communication, asuperset cell being determined to be also a subset cell if: thatsuperset cell is known to have the capability of also being a subsetcell; and, the number of existing subset cells is below a predeterminedmaximum number of subset cells; and, following the determining steps,storing information on each cell as to whether the category of the cellis in-range cell, superset cell, subset-capable cell or subset cell,that information being used for determining what to include in the nextpower measurement.

Preferably, a superset cell is only determined to be also a subset cellif, additionally, the UE-received pilot-signal power of that supersetcell is above a subset power threshold different from the superset powerthreshold.

In one form of another aspect, the subject invention provides a methodfor Universal Mobile Telecommunications System (UMTS) communicationutilizing User Equipment (UE) and a Radio Network Controller (RNC) forcommunicating with the UE through a changing set of cells. The methodincludes periodically performing the steps of: measuring at the UE thepower in received pilot signals from in-range cells; deter-mining whichof in-range cells are to be included in communication to the UE(superset cells), an in-range cell being determined to be a supersetcell if the UE-received pilot-signal power is above a superset powerthreshold; determining whether any of the superset cells is also asubset cell capable of providing enhanced UE communication, a supersetcell being determined to be also a subset cell if: that superset cell isknown to have the capability of also being a subset cell; and, theUE-received pilot-signal power of that superset cell is above a subsetpower threshold different from the superset power threshold.

The method may include the further step of using the determined resultfor determining what to include in the next power measurement at the UE.

In another form, the subject invention provides a method performed by aRadio Network Controller of a Universal Mobile Telecommunications System(UMTS). The method includes periodically performing the steps of:receiving from User Equipment (UE) measurement of power in pilot signalsof cells; determining which of in-range cells are to be included incommunication to the UE (superset cells), an in-range cell beingdetermined to be a superset cell if the UE-received pilot-signal poweris above a superset power threshold; determining whether any of thesuperset cells is also a subset cell capable of providing enhanced UEcommunication, a superset cell being determined to be also a subset cellif: that superset cell is known to have the capability of also being asubset cell; and, the UE-received pilot-signal power of that supersetcell is above a subset power threshold different from the superset powerthreshold.

The method may further include the step of transmitting the determinedresult to the UE. The determined result may include information on eachcell as to whether the category of the cell is in-range cell, supersetcell, subset-capable cell or subset cell, that information being used bythe UE for determining what to include in the next power measurement.

In a further form, the subject invention provides a method performed byUser Equipment (UE) of a Universal Mobile Telecommunications System(UMTS). The method includes periodically performing the steps of:measuring power in pilot signals of cells, the measurement allowing for:determining which of in-range cells are to be included in communicationto the UE (superset cells), an in-range cell being determined to be asuperset cell if the UE-received pilot-signal power is above a supersetpower threshold; and, determining whether any of the superset cells isalso a subset cell capable of providing enhanced UE communication, asuperset cell being determined to be also a subset cell if: thatsuperset cell is known to have the capability of also being a subsetcell; and, the UE-received pilot-signal power of that superset cell isabove a subset power threshold different from the superset powerthreshold; and, following the determining steps, storing information oneach cell as to whether the category of the cell is in-range cell,superset cell, subset-capable cell or subset cell, that informationbeing used in the next power measuring.

Preferably, a superset cell is only determined to be also a subset cellif, additionally, the number of existing subset cells is below apredetermined maximum number of subset cells.

The predetermined maximum number of subset cells may be one, two orthree less than the number of superset cells.

The superset power threshold may be a lower value of a superset definedrange of power having as an upper value the pilot-signal power of thein-range cell that is measured to have the highest received power fromamong the in-range cells.

The subset power threshold may be a lower value of a subset definedrange of power having as an upper value the pilot-signal power of thein-range cell that is measured to have the highest received power fromamong the in-range cells. Alternatively, the subset power threshold maybe determined as follows. For the superset cell determined firstly to bealso a subset cell (first subset cell), the subset power threshold isone of: (i) the power level of a subset-capable cell having the highestpower level in the superset, and (ii) a predetermined power value; and,for the superset cells subsequently determined to be also subset cells,the subset power threshold is a lower value of a second defined range ofpower having as an upper value the pilot-signal power of the subset cellthat is measured to have the highest received power.

The method may also include the steps of: communicating between the UEand the RNC by using the superset cells; and, if any of the supersetcells is determined to be also a subset cell, adding enhanced UEcommunication to existing UE communication on that cell.

The method may also include the steps of: communicating between the UEand the RNC by using the superset cells; and, if at least one of thesuperset cells is determined to be also a subset cell, changing thecommunication such that: a maximum of four cells are used in the UEcommunication; and, those of the cells that are subset cells utilize theenhanced UE communication.

The superset cells may include: six or less cells if none of thesuperset cells is also a subset cell; and, four or less cells if atleast one of the superset cells is also a subset cell.

In the method, the RNC may have knowledge of which of the superset cellshas the capability of also being a subset cell, and the RNC thenperforms the determining steps based on that knowledge and based on thepilot-signal power measurements which are made at the UE and forwardedto the RNC by the UE.

The enhanced UE communication may be UE communication at higher datarates and/or higher transmission intervals.

The higher data rates may be in the range of 200 to 1200kilobits/second.

The enhanced UE communication may involve only uplink communication fromthe UE.

The superset defined range of power may be 4 dB. The subset definedrange of power may be 2 dB.

The method may include the further step of: placing the superset cellsin order of power level, extending from the superset cell with thehighest measured pilot-signal power level in the superset defined rangeof power to the superset cell with the lowest measured pilot-signalpower level in that range.

The method may include the further step of: placing the subset cells inorder of power level, extending from the subset cell with the highestmeasured pilot-signal power level in the subset defined range of powerto the subset cell with the lowest measured pilot-signal power level inthat range.

In any of the preceding methods, power and power level are measured interms of: Signal-to-Noise Ratio (SNR); Path Loss; or, Signal Strength.

In one form of a still further aspect, the subject invention provides aUniversal Mobile Telecommunications System (UMTS) system that includes:User Equipment (UE) including means for measuring the power in receivedpilot signals from in-range cells; a Radio Network Controller (RNC) thatincludes: means for receiving information on the power measurements fromthe UE; means for determining which of in-range cells are to be includedin communication to the UE (superset cells), an in-range cell beingdetermined to be a superset cell if the UE-received pilot-signal poweris above a superset power threshold, and for determining whether any ofthe superset cells is also a subset cell capable of providing enhancedUE communication, a superset cell being determined to be also a subsetcell if: that superset cell is known to have the capability of alsobeing a subset cell; and, the number of existing subset cells is below apredetermined maximum number of subset cells.

The UMTS system may further include means for transmitting thedetermined result to the UE, and may further include means for using thedetermined result for determining what to include in the next powermeasurement.

In another form, the subject invention provides a Radio NetworkController (RNC) of a Universal Mobile Telecommunications System (UMTS),the RNC including: means for receiving from User Equipment (UE)measurement of power in pilot signals of cells; and, means fordetermining: which of in-range cells are to be included in communicationto the UE (superset cells), an in-range cell being determined to be asuperset cell if the UE-received pilot-signal power is above a supersetpower threshold, and determining whether any of the superset cells isalso a subset cell capable of providing enhanced UE communication, asuperset cell being determined to be also a subset cell if: thatsuperset cell is known to have the capability of also being a subsetcell; and, the number of existing subset cells is below a predeterminedmaximum number of subset cells.

The RNC may further include means for transmitting the determined resultto the UE. The determined result may include information on each cell asto whether the category of the cell is in-range cell, superset cell,subset-capable cell or subset cell, that information being used in thefollowing measurement of power by the UE.

In a further form, the subject invention provides User Equipment (UE) ofa Universal Mobile Telecommunications System (UMTS), the UE including:means for measuring power in cell pilot signals, the measurementallowing for: determining which of in-range cells are to be included incommunication to the UE (superset cells), an in-range cell beingdetermined to be a superset cell if the UE-received pilot-signal poweris above a superset power threshold, and determining whether any of thesuperset cells is also a subset cell capable of providing enhanced UEcommunication, a superset cell being determined to be also a subset cellif: that superset cell is known to have the capability of also being asubset cell; and, the number of existing subset cells is below apredetermined maximum number of subset cells; and, means for, followingthe determining steps, storing information on each cell as to whetherthe category of the cell is in-range cell, superset cell, subset-capablecell or subset cell, that information being used in the following powermeasurement.

Preferably, a superset cell is only determined to be also a subset cellif, additionally, the UE-received pilot-signal power of that supersetcell is above a subset power threshold different from the superset powerthreshold.

In one form of a yet further aspect, the subject invention provides aUniversal Mobile Telecommunications System (UMTS) that includes: UserEquipment (UE) including means for measuring the power in received pilotsignals from in-range cells; a Radio Network Controller (RNC) including:means for receiving information on the power measurements from the UE;means for determining which of in-range cells are to be included incommunication to the UE (superset cells), an in-range cell beingdetermined to be a superset cell if the UE-received pilot-signal poweris above a superset power threshold, and for determining whether any ofthe superset cells is also a subset cell capable of providing enhancedUE communication, a superset cell being determined to be also a subsetcell if: that superset cell is known to have the capability of alsobeing a subset cell; and, the UE-received pilot-signal power of thatsuperset cell is above a subset power threshold different from thesuperset power threshold.

The UMTS system may further include means for transmitting thedetermined result to the UE, and may still further include means forusing the determined result for determining what to include in the nextpower measurement.

In another form, the subject invention provides a Radio NetworkController (RNC) of a Universal Mobile Telecommunications System (UMTS),the RNC including: means for receiving from User Equipment (UE)measurement of power in pilot signals of cells; means for: determiningwhich of in-range cells are to be included in communication to the UE(superset cells), an in-range cell being determined to be a supersetcell if the UE-received pilot-signal power is above a superset powerthreshold, and determining whether any of the superset cells is also asubset cell capable of providing enhanced UE communication, a supersetcell being determined to be also a subset cell if: that superset cell isknown to have the capability of also being a subset cell; and, theUE-received pilot-signal power of that superset cell is above a subsetpower threshold different from the superset power threshold.

The RNC may further include means for transmitting the determined resultto the UE. The determined result may include information on each cell asto whether the category of the cell is in-range cell, superset cell,subset-capable cell or subset cell, that information being used in thefollowing measurement of power by the UE.

In a further form, the subject invention provides User Equipment (UE) ofa Universal Mobile Telecommunications System (UMTS), the UE including:means for measuring power in pilot signals of cells, the measurementallowing for: deter-mining which of in-range cells are to be included incommunication to the UE (superset cells), an in-range cell beingdetermined to be a superset cell if the UE-received pilot-signal poweris above a superset power threshold, and determining whether any of thesuperset cells is also a subset cell capable of providing enhanced UEcommunication, a superset cell being determined to be also a subset cellif: that superset cell is known to have the capability of also being asubset cell; and, the UE-received pilot-signal power of that supersetcell is above a subset power threshold different from the superset powerthreshold; and, means for, following the determining steps, storinginformation on each cell as to whether the category of the cell isin-range cell, superset cell, subset-capable cell or subset cell, thatinformation being used in the following power measurement.

Preferably, in the UMTS system, RNC or UE, a superset cell is onlydetermined to be also a subset cell if, additionally, the number ofexisting subset cells is below a predetermined maximum number of subsetcells.

Preferably, in the UMTS system, RNC, or UE, the predetermined maximumnumber of subset cells is one, two or three less than the number ofsuperset cells.

Preferably, in the UMTS system, RNC or UE, the superset power thresholdis a lower value of a superset defined range of power having as an uppervalue the pilot-signal power of the in-range cell that is measured tohave the highest received power from among the in-range cells. And morepreferably, the subset power threshold is a lower value of a subsetdefined range of power having as an upper value the pilot-signal powerof the in-range cell that is measured to have the highest received powerfrom among the in-range cells. Alternatively, more preferably: for thesuperset cell first determined to be also a subset cell (first subsetcell), the subset power threshold is one of: (i) the power level of asubset-capable cell having the highest power level in the superset, and(ii) a predetermined power value; and, for the superset cellssubsequently determined to be also subset cells, the subset powerthreshold is a lower value of a second defined range of power having asan upper value the pilot-signal power of the subset cell that ismeasured to have the highest received power.

The UMTS system, RNC or UE may further include: means for communicatingbetween the UE and the RNC by using the superset cells; and, means for,if any of the superset cells is determined to be also a subset cell,adding enhanced UE communication to existing UE communication on thatcell.

The UMTS system, RNC or UE may further include: means for communicatingbetween the UE and the RNC by using the superset cells; and, means for,if at least one of the superset cells is determined to be also a subsetcell, changing the communication such that: a maximum of four cells areused in the UE communication; and, those of the cells that are subsetcells utilize the enhanced UE communication.

In the UMTS system, RNC or UE, the superset cells may include: six orless cells if none of the superset cells is also a subset cell; and,four or less cells if at least one of the superset cells is also asubset cell.

In the UMTS system, RNC or UE, the RNC may have knowledge of which ofthe superset cells has the capability of also being a subset cell, withthe RNC performing the determining steps based on that knowledge andbased on pilot-signal power measurements which are made at the UE andforwarded to the RNC by the UE.

In the UMTS system, RNC or UE, the enhanced UE communication may be UEcommunication at higher data rates and/or higher transmission intervals.Those higher data rates may be in the range of 200 to 1200kilobits/second. The enhanced UE communication may be uplinkcommunication from the UE. The superset defined range of power may be 4dB. The subset defined range of power may be 2 dB.

The UMTS system, RNC or UE may further include: means for placing thesuperset cells in order of power level, extending from the superset cellwith the highest measured pilot-signal power level in the supersetdefined range of power to the superset cell with the lowest measuredpilot-signal power level in that range.

The UMTS system, RNC or UE may further include: means for placing thesubset cells in order of power level, extending from the subset cellwith the highest measured pilot-signal power level in the subset definedrange of power to the subset cell with the lowest measured pilot-signalpower level in that range.

In the UMTS system, RNC or UE, power and power level may be measured interms of: Signal-to-Noise Ratio (SNR); Path Loss; or, Signal Strength.

BRIEF DESCRIPTION OF DRAWING

Preferred features of the present invention will now be described, byway of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 shows the equations involved in determining the Events 1a and 1b,and indicates the factors involved in that determination;

FIG. 2 shows the relationship between in-range cells, superset cells andsubset cells;

FIG. 3 is a graph of cell strength with time, the graph illustrating atriggering of an Event 1c′; and

FIG. 4 illustrates a UMTS system including the UE and RNC of thedisclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

Although a UE is able to communicate with its RNC through a maximum ofsix cells when none of the cells is an E-DCH cell, i.e. all are DCH,that maximum number of cells drops to four cells if one of the DCH cellsbecomes also an E-DCH cell. Whether a cell can transition from being aDCH cell to an E-DCH cell is dependent upon several factors. Firstly,the DCH cell has to be associated with a nodeB that has been upgraded topass enhanced communication to the RNC. The RNC keeps a record of allthe nodeBs under its control that have the E-DCH capability. Secondly,the first form of subject invention requires that the number of E-DCHcells already in use at the UE be below a predetermined maximum number.Based on measurements that are forwarded to the RNC by the UE on thesecond factor, the RNC determines whether a DCH cell of a UE can becomean E-DCH cell. It should be noted that in UMTS each UE typically sendsan updated set of power measurements to its RNC when a particular eventis triggered.

First Embodiment

FIG. 3 relates to an example of a first embodiment of the subjectinvention. The first aspect relates to a situation in which a UE ispassing through a mix of E-DCH and non-E-DCH cells or through E-DCHcells only, and where the maximum Active Set size for DCH is larger thanE-DCH. The example here involves a maximum Active Set size for DCH of 4(4 instead of 6 applying here, since at least one E-DCH cell alreadyexists); it also involves a predetermined maximum Active Set size forE-DCH of 3. The maximum Active Set size for E-DCH could be set to 2 oreven to 1. In the first embodiment, E-DCH cells are added until thepredetermined maximum Active Set size is reached.

Once the maximum number is reached, an Event 1c′ (FIG. 3) is required toreplace one of the E-DCH cells (usually the E-DCH cell with the lowestpower) with another E-DCH cell. (Note that Event 1c represents anexchange of a superset cell with another cell not in the superset,whereas an Event 1c′ represents an exchange of a subset cell withanother cell not in the subset.) The sequence of Events, as shown inFIG. 3, are:

-   -   1. DCH (Active Set)=(A*, B*, C*, D*)        -   E-DCH Active Set=(A, B, C)    -   2. DCH (Active Set)=(A*, B*, D*, C*)        -   E-DCH Active Set=(A, B, D)

In this situation, the new Event 1c′ is triggered to replace cell C inthe E-DCH Active Set with cell D of the E-DCH Active Set.

In the above example and those that follow, * indicates possiblemembership of the subset and the sequence “A, B, C, D, E” indicates theordering of the cells according to their respective strength, i.e. cellA is the strongest and cell E is the weakest.

A second example of the first embodiment involves a more complicatedsituation, in which any of the new Events 1a′, 1b′ and 1c′ can occur(respectively, adding, removing and exchanging cells). Rules to addcells to the subset are independent of rules to add cells to thesuperset. A typical sequence of Events in this case is the following:

-   -   1. DCH (Active Set)=(A, C*, B, D*)        -   E-DCH Active Set=(C)    -   Comment: Cell D quality is not good enough to become a member of        the E-DCH Active Set.    -   2. DCH (Active Set)=(A, C*, D*, E*)        -   E-DCH Active Set=(C, D)    -   Comment: Cell D quality has improved, triggering Event 1a′ to        add cell D to the E-DCH Active Set.    -   3. DCH (Active Set)=(C*, E*, D*, F*)        -   E-DCH Active Set=(C, E, D)    -   Comment: New Event 1a′ has been triggered to add Cell E to the        E-DCH Active Set.    -   4. DCH (Active Set)=(F*, C*, E*, D*)        -   E-DCH Active Set=(F, C, E)    -   Comment: New Event 1c′ has been triggered to replace Cell D with        Cell F in the E-DCH Active Set.    -   5. DCH (Active Set)=(F* C*, E*, D*)        -   E-DCH Active Set=(F, C)    -   Comment: New Event 1b′ has been triggered to remove Cell E from        the E-DCH Active Set.

The E-DCH Serving Cell, i.e. the E-DCH cell that is currently in use atany time is typically the one that is the E-DCH Active Set cell with thebest quality. Such best cell can be determined by using an Event 1dmeasurement for the cells in the E-DCH Active Set.

The next example relates to a situation where the DCH Active Set ofcells and the E-DCH Active set of cells, i.e. the superset and subset ofcells, are interacting. In this case the UE is able to identify thesuperset cells with subset-call capability (“subset-capable cells”) fromthe subset cells and to take power measurements of cells which the UEknows are within the subset as well as power measurements of cells thatit knows are subset-capable (though not actually within the subset).

-   -   1. DCH (Active Set)=(C*, B)        -   E-DCH Active Set=(C)    -   2. DCH (Active Set)=(C*, B, A)        -   E-DCH Active Set=(C)    -   Comment: Cell A is an in-range cell whose power has increased,        and this triggers Event 1a to add Cell A to the DCH Active Set        (but not to the E-DCH Active Set).    -   3. DCH (Active Set)=(C*, B, A, E*)        -   E-DCH Active Set=(C)    -   Comment: Cell E is an in-range cell whose power has increased,        and this triggers Event 1a to add Cell E to the DCH Active Set        (but not to the E-DCH Active Set).    -   4. DCH (Active Set)=(B, C*, E*,        -   E-DCH Active Set=(C, E)    -   Comment: Cell E power has increased, triggering an Event 1a′ to        add Cell E to the E-DCH Active Set.    -   5. DCH (Active Set)=(B, C*, A, E*)        -   E-DCH Active Set=(C)    -   Comment: Cell E power has decreased, triggering Event 1b′ to        remove Cell E from the E-DCH Active Set.    -   6. DCH (Active Set)=(B, C*, E*,        -   E-DCH Active Set=(C, E)    -   Comment: Cell E power has increased, triggering Event 1a′ to add        Cell E to the E-DCH Active Set.    -   7. DCH (Active Set)=(B, C*, E*, F*)        -   E-DCH Active Set=(C, E)    -   Comment: Cell A power has become less than Cell F, triggering        Event 1c to replace Cell A with Cell F in the DCH Active Set        (Cell F is not in the E-DCH Active Set).    -   8. DCH (Active Set)=(B, C*, E*, F*)        -   E-DCH Active Set=(C, E, F)    -   Comment: Cell F power has increased, triggering Event 1a′ to add        Cell F to the E-DCH Active Set.    -   9. DCH (Active Set)=(C*, F*, E*, D*)        -   E-DCH Active Set=(C, F, E)    -   Comment: Cell B power has decreased below that of Cell D,        triggering Event 1c to replace Cell B with Cell D in the DCH        Active Set.    -   10. DCH (Active Set)=(F*, D*, E*, C*)        -   E-DCH Active Set=(F, D, E)    -   Comment: Cell C power has become less than Cell D in the E-DCH        Active Set, triggering Event 1c′ to replace Cell C with Cell D        in the E-DCH Active Set.    -   11. DCH (Active Set)=(F*, D*, E*, C*)        -   E-DCH Active Set=(F, D)    -   Comment: Cell E power has decreased, triggering Event 1b′ to        remove Cell E from the E-DCH Active Set.    -   12. DCH (Active Set)=(F*, D*, E*)        -   E-DCH Active Set=(F, D)    -   Comment: Cell C power has decreased, triggering Event 1b to        remove Cell C from the DCH Active Set.

Second Embodiment

A second embodiment of the subject invention relates to the E-DCH ActiveSet of cells having a different power threshold from the power thresholdof the DCH Active Set of cells. A UMTS might utilize the firstembodiment in combination with the second embodiment to be described, ormight use only one of them.

When the RNC determines that one of the superset cells meets thecriteria for becoming a first subset cell, it conveys this informationto the UE. The UE then recognizes that superset cell as also being asubset cell during the next power measurement. Conventional UEs did notrecognize which of the superset cells were also subset cells, so thereobviously existed no need for the UEs to consider whether a differentpower threshold should apply to subset cells than the power thresholdapplied to superset cells. However, with the UE of the subject inventionable to distinguish between superset cells and subset cells, it ispossible to consider the application of a different power threshold toeach. This is a desirable feature for the following reason. The subnetcells operate at a faster data rate or a shorter interval betweentransmissions. Therefore, to maintain quality at the faster speed, it isimportant that the transmitted information in subset cells betransmitted with better quality if possible. In turn, better qualityrequires that each subset cell be required to be within a small powerband, i.e. a smaller power threshold.

What is proposed is that, if for instance the power threshold of thesuperset cells is set at 4 dB, the power threshold of the subset cellsis set at say 2 dB. All cells in the E-DCH Active Set have to have apower level that is within 2 dB of each other, and this needs to bemeasured from the power of the subset cell that has the highest powervalue. That presents a problem, however, if the subset cell is the firstsubset cell. In that special case, the first subset call is selected if:(i) the power level of the candidate subset cell is the highest powerlevel in the superset, or (ii) the power level of the candidate subsetcell is above a predetermined power level separate from the cell powerlevels. If either criteria is met, the particular cell becomes the firstsubset cell, and the E-DCH Active Set is created with the particularcell as first member. If the UE is then advised that a second supersetcell is capable of becoming a subset cell, the measurement next made isthe power level of the particular cell now in the E-DCH Active Set. Ifthe second potential subset cell has a power 2 dB or less below thepower level of the particular cell, then the second cell joins theparticular cell in the E-DCH Active Set. This continues until themaximum number allowed in the E-DCH Active Set is reached, after whichEvents 1c′ are required to maintain the E-DCH Active Set at or below itsmaximum size. That maximum size could be the whole superset, althoughthe first embodiment dealt with a situation in which the number of cellsin the E-DCH Active Set (subset cells) is always maintained at one lessthan the number of cells in the DCH Active Set (superset cells).

It is of course possible that, although the subset is capable of havinga different power threshold than the superset, it is desirable tomaintain both at the same power threshold, i.e. 4 dB. This results in asimpler situation, but one still within the scope of the subjectinvention.

While the present invention has been described in its preferredembodiments, it is to be understood that the words which have been usedare words of description rather than limitation, and that changes may bemade to the invention without departing from its scope as defined by theclaims.

Each feature disclosed in this specification (which term includes theclaims) and/or shown in the drawings may be incorporated in theinvention independently of other disclosed and/or illustrated features.

A Universal Mobile Telecommunications System (UMTS) allows UserEquipment (UE) to distinguish between superset cells which are alsosubset cells and superset cells which are not. Subset cells in UMTS arecells associated with system nodes that allow enhanced communicationsuch as, for instance, faster data rates or smaller intervals betweentransmissions. The ability to distinguish between superset cells andsubset cells allows UE to adjust its next set of power measurements ofcells to capture power level changes among subset cells as well as amongsuperset cells. Conventional UEs are only capable of knowing thedifference between superset cells and cells that are in-range. Theadvantage of the UE knowing which superset cells are also subset cellsor subset-capable cells is that the UE can provide extra information tohelp the RNC determine which cells to use for enhanced communication.Downlink communication to UEs is already at high speeds; the subjectinvention will provide a means for similar increases in uplinkcommunication from UEs. A RNC and UE for operation in the UMTS areincluded in the invention.

1-29. (canceled)
 30. User equipment for a Universal MobileTelecommunications System, UMTS, mobile communication system, the UMTSmobile communication system defining a dedicated channel ‘DCH’ activeset and an enhanced-dedicated channel ‘E-DCH’ active set, the userequipment comprising: a circuit for performing a power measurement of apilot signal from a first cell that is not included in the E-DCH activeset but included in the DCH active set; a circuit for performing a powermeasurement of a pilot signal from a second cell that is included in theE-DCH active set; a circuit for determining that an event has beentriggered when said power measurement of a pilot signal from said secondcell has become less than said power measurement of a pilot signal fromsaid first cell; and a circuit for sending results of said powermeasurements towards a radio network controller of the UMTS mobilecommunication system when said event has been triggered.
 31. The userequipment according to claim 30, wherein the E-DCH has a higher datarate than a data rate of the DCH.
 32. The user equipment according toclaim 30, wherein the E-DCH is utilized for an uplink communication fromthe user equipment.
 33. The user equipment according to claim 30,further comprising a circuit for receiving information as to which cellis to be in the E-DCH active set from the radio network controller inthe mobile communication system.
 34. The user equipment according toclaim 30, further comprising a circuit for sending information on thepower measurement of the pilot signal from the cell that is not includedin the E-DCH active set but included in the DCH active set and the pilotsignal from the cell included in the E-DCH active set.
 35. A method fora Universal Mobile Telecommunications System, UMTS, mobile communicationsystem, the UMTS mobile communication system defining a dedicatedchannel ‘DCH’ active set and an enhanced-dedicated channel ‘E-DCH’active set, the method comprising: performing a power measurement of apilot signal from a first cell that is not included in the E-DCH activeset but included in the DCH active set; performing a power measurementof a pilot signal from a second cell that is included in the E-DCHactive set; determining that an event has been triggered when said powermeasurement of a pilot signal from said second cell has become less thansaid power measurement of a pilot signal from said first cell; andsending results of said power measurements towards a radio networkcontroller of the UMTS mobile communication system when said event hasbeen triggered.
 36. The method according to claim 35, wherein the E-DCHhas a higher data rate than a data rate of the DCH.
 37. The methodaccording to claim 35, wherein the E-DCH is utilized for an uplinkcommunication from user equipment.
 38. The method according to claim 35,further comprising receiving, at the user equipment, information as towhich cell is to be in the E-DCH active set from the radio networkcontroller in the mobile communication system.
 39. The method accordingto claim 35, further comprising sending information on the powermeasurement of the pilot signal from the cell that is not included inthe E-DCH active set but included in the DCH active set and the pilotsignal from the cell that is included in the E-DCH active set.